The literal meaning of feral is "gone wild" . When used to describe a cat it usually means that they have either been born in the wild or have been lost or abandoned and have reverted to the wild. 
Feral cats may have very limited experience of human contact and so will generally keep away from people and run away if you try to approach them. However, as long as the cat is not too old, it is possible that they will eventually become very loving pets, if approached correctly, but be warned it can take weeks or months of gentle persuasion and patience on your part before a feral cat may feel comfortable enough to be a part of your family.